Drilling systems are frequently used to provide cylindrical holes in metallic workpieces. The cutting or boring action of the drill system may be carried out by an elongated, substantially cylindrical drilling tool, such as a combination of a tool holder and a drill insert, which is selectively attached thereto. Such an arrangement may then be used in an application wherein one end of the tool holder is securely mounted in a driving apparatus, which rotates the holder about its longitudinal axis. At the opposite end of the elongated tool holder, the cutting insert engages the material to be cut. Alternatively, the workpiece may be made to rotate relative to the holder and cutting insert, such as in positioning the holder in the tail stock of a lathe or the like. Further, the tool and workpiece may be made to rotate relative to one another. The use of cutting inserts allows for quick changing of the insert upon wear of the cutting surfaces instead of the entire tool, and allows for one tool to be used for a variety of different boring applications by simply changing the insert and not the entire drill assembly.
However, one particular application which provides problems for prior art cutting tools involves drilling holes through the web portion of structural steel I beams, for example. The flanges of the I-beam require the tool to reach a significant distance to the web of the I-beam. The reach distance can cause a severe instability problem for the tool when attempting to cut a hole through the web. As a result, the tool may wobble or “walk” resulting in an oversize hole, run-out, bellmouthing, and/or an off location hole. Another problem is that the web in these applications are typically relatively thin. During the drilling process, the drill pressure pushes against the thin wall of material allowing it to deflect. As the tool breaks through the material, the material snaps back to its original position, resulting in an irregular shaped hole. Still another problem presented by this and similar applications is that a large burr is produced on the backside of the material. As the tool breaks through the material, the built up drilling pressure causes the tool to lunge through the drilled hole which results in the creation of a burr on the backside of the material. This typically requires an added de-burring process to the machining operation in order to remove the burr. In applications such as with structural steel it is critical that not only the hole be round, but that there is no burr to interfere between the register surfaces of beams and connector plates which must lay flat when they are being connected. A burr can result in an improper connection length and also decrease the strength of the connection by preventing a proper preload of the fastener used to connect the beams.